September 11, 2008

Freshwater Fish Species Dwindling In North America

A recent study reports that nearly 40 percent of freshwater fish species in North America are in trouble, doubling since 1989.

According to experts, humans have caused the "silent extinctions" through polluting and damming freshwater habitats.

In the first large study of freshwater fish in North America in 19 years, a team of researchers from the US, Canada, and Mexico looked at a species restricted to certain geographic areas.  The decline among these "subspecies" groups is even more drastic.

Researchers found that 700 individual fish populations are threatened of endangered, up 364 subspecies from 1989 reports.

The study, published by the American Fisheries Society, found that 457 species might already be extinct.

The group of researchers looked at thousands of individual fish populations living in lakes, steams, rivers, or those that live in saltwater but migrate to freshwater, like salmon.

They found a number species to be vulnerable including the snail bullhead, flat bullhead, spotted bullhead catfish, sockeye, Chinook, Coho, chum and the Atlantic salmon.  More than 24 populations of trout are also considered to be in danger.

According to the study's lead author Howard Jelks, one third of the populations that were in peril in 1989 have worsened while 6 percent have made a comeback.

Jelks said the number of species in trouble was more that he expected and is far more that those on the US government's endangered species list.

Jelks blames degraded freshwater habitat, and invasive species for the increase in vulnerable species.

Fish "live in a freshwater habitat that's pretty much under assault by people," said Larry Crowder, a Duke University marine biologist. "Things are tanking all around us. When does it have to be bad enough to get people's attention?"

Many of the vulnerable species are small minnows that can easily go unnoticed but are a vital part of the food chain.

In Mexico nearly half the fish species are in trouble.  One third of fish in the US are in trouble, while only 10 percent of fish in Canada are dwindling. 

Anthony Ricciardi, a McGill University biologist found that freshwater extinctions were happening at a faster pace than on the land or in the sea, yet few people noticed.

"A lot of silent extinctions are happening," said Ricciardi. "What we're doing is widespread, it's pervasive and it's rapid."


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